class Solution:
    def maximumTime(self, time: str) -> str:
        t = list(time)
        if t[0] == '?':
            t[0] = '1' if '4' <= t[1] <= '9' else '2'
        if t[1] == '?':
            t[1] = '3' if t[0] == '2' else '9'
        if t[3] == '?':
            t[3] = '5'
        if t[4] == '?':
            t[4] = '9'
        return ''.join(t)
